Effectively offering more than 100% financing.  

Your referencing effective age vs chronological age. 

@Anthony Finelli check your mortgage paperwork for the Truth-In-Lending form to find your APR.APR is your effective interest rate including interest, MIP and closing costs.If you can refinance the rental at a cheaper rate than the APR, then you should!

I own a 30-unit community and found it much easier and more cost effective than the 1-4 family and flips that I was doing before that acquisition. 

Should I make an offer with the qualification that all furnishings, dishes, pots, and pans stay, except for "personal" effects?

Sub2 is a risky strategy for a long term buy and hold as the longer the deal structure stays in place, the higher the chance that issues will arise (like issues with the loan servicer, insurance, seller filing for bankruptcy, seller dying, seller realizing their DTI ratio and ability to buy their next property is negatively effected and becoming upset about it like in your case, due on sale clause being called, etc.).

I completely agree with @Ashish Acharya's points about the cost-effectiveness of a HELOC and the potential credit implications if it’s secured by your primary residence.

Point is the above comments there are many other more effective ways to meet the FINCEN stated objectives for tax evasion, money laundering and terrorism.   

The tenant has not paid anything since April 2024, effectively staying in my property for free for four months.

However, the most effective method is to simply tell the tenant that they'll need to provide proof of insurance prior to or on the day 1 of the start of the lease, otherwise the keys will not be provided to them.